Dreams about sweeping often symbolize a desire to clean up or clear out aspects of your life. In your case, sweeping a dusty veranda may indicate that you are feeling overwhelmed by situations or people around you, particularly in relation to your future family or in-laws, given the context of your dream. It might suggest a need for you to take control of your surroundings or to address issues that have been neglected.

The presence of charcoal dust could represent something that has left a mark or residue in your life, possibly reflecting feelings of frustration or disappointment, especially if you feel that others are not contributing to maintaining a clean or harmonious environment.

Seeing yourself sweeping while your in-laws are sitting nearby may point to your concerns about your future relationship and the dynamics within that family. It could indicate a desire to prove yourself or to maintain peace and cleanliness in your prospective family life.

Overall, this dream might be encouraging you to address any unresolved issues, to communicate openly with your partner and their family, and to take an active role in shaping the environment you want to be part of. Consider reflecting on what specific feelings or situations in your life might need "sweeping up" or addressing.